import gc

class TestClass(object):
    outer = []
    def __init__(self):
        self.inner = []

for num in range(10):
    test = TestClass()
    test.outer.append("pass: {}".format(num))
    test.inner.append("pass: {}".format(num))
    test = None
    gc.collect()

test = "blah"
test = TestClass()
print(test.outer)
print(test.inner)